Quo vadis, neutrino flavor models. Stefano Morisi Università Federico II di Napoli, INFN sez. Napoli

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1 Quo vadis, neutrino flavor models Stefano Morisi Università Federico II di Napoli, INFN sez. Napoli

2 The flavor problem t Mass hierarchy? Mixing hierarchy? b e d u mu c tau s why 3 generations? origin of neutrino mass?

3 The flavor problem t Mass hierarchy? Mixing hierarchy? b e d u mu c tau s why 3 generations? origin of neutrino mass?

4 The flavor problem Mass hierarchy? Mixing hierarchy? Is the flavor problem the evidence of some underlying symmetry? why 3 generations? origin of neutrino mass?

5 Flavor symmetry u d c s t b SU(2) gauge doublet e triplet irreducible representation of a flavor group?

6 Lepton mixing: status M, proceeding NOW12 large solar large atmospheric small reactor Is the atmospheric angle maximal? Reactor angle not zero!

7 Is the atmospheric angle maximal? Yes No With abelian flavor symmetry difficult to get maximal mixings Strong indications in favor of non abelian flavor symmetry everything is possible: there are no particular indication on the flavor symmetry...

8 maximal mixing & mu-tau symmetry exchange symmetry In the neutrino sector Babu, Ma, Valle 02 Grimus, Lavoura, 04 Altarelli, Feruglio 05 Caravaglios, M, exchange symmetry broken in the charged sector

9 maximal mixing & mu-tau symmetry Difficult to get because exchange symmetry In the neutrino sector ( ) exchange symmetry broken in the charged sector

10 maximal atmospheric mixing origin of mu-tau neutrino symmetry A4 Non-abelian symmetry Symmetry of tetrahedron Triplet representation Finite subgroup of SU(3) Broken in the charged lepton sector: but Z3 preserved In the neutrino sector

11 maximal atmospheric mixing and reactor angle M, Patel, Peinado 11 Boucenna, M, Tortola, Valle 11 King, 12 King, Luhn 12 We expect deviations of the exchange symmetry in the neutrino sector

12 What if the atmospheric angle is not maximal?

13 Anarchy: neutrino mass matrix has random entries M=m( O(1) O(1) O(1) ) O(1) O(1) O(1) O(1) O(1) O(1) Hall, Murayama, Weiner 99 implies mixing and ratio of masses of order one in rough agreement with data

14 discrete non abelian symmetries so far are not excluded connection between atmospheric and reactor angles, i.g. mixing sum rule Ballet, King, Luhn, Pascoli, Schmidt 13

15 Discrete symmetries & Mass sum rules Altarelli, Feruglio, Hagedorn 08 Hirsch, M, Valle 08 Bazzocchi, M, Merlo 09 Altarelli, Meloni 09 Barry, Rodejohann 10/11 Dorame, Meloni, M, Peinado,Valle11 See talk of Merle

16 Mass sum rules & 0nubb King, Merle, M, Shimizu, Tanimoto 14 See talk of Merle

17 Flavor symmetries: multi-higgs vs flavon

18 Flavor symmetries: multi-higgs vs flavon No signal at LHC,...

19 Flavor symmetries: multi-higgs vs flavon New Higgs at the weak scale FCNC, LFV,... Flavor symmetry gives relations between branching ratios See talk of Vicente

20 Higgs decay and flavor symmetry, i.g. Heeck et al, Based on A4: it is distinguishable and falsifiable See also: triality, Ma PRD (10) Higgs decay in S3, Bhattacharyya et al PRD (12)

21 Lepton non-universality and flavor symmetry R = 1 in the SM Only 2,6 sigma LHCb collaboration PRL (14)

22 Lepton non-universality and flavor symmetry Only 2,6 sigma LHCb collaboration PRL (14) Minimal Flavor Violation: Alonso et al Lee, Tandeon Z' Celis et al Crivellin et al Neutrino oscillation Boucenna et al

23 Lepton non-universality and flavor symmetry Leptoquark Hiller, Schmaltz JHEP (15) SU(2) doublet SU(2) triplet

24 Lepton non-universality and flavor symmetry Non-Abelian flavor symmetry De Medeiros, Hiller

25 Flavor symmetries: from neutrino to quarks While large neutrino mixing seems to give indication of non-abelian family symmetry Typically the neutrino flavor symmetries do not naturally fit the quark sector Non abelian symmetries must be introduced to fit also the quark sector

26 Flavor symmetries: from neutrino to quarks While large neutrino mixing seems to give indication of non-abelian family symmetry Typically the neutrino flavor symmetries do not naturally fit the quark sector Non abelian symmetries must be introduced to fit also the quark sector The problem is to find a simple common framework

27 GUT LHC DM Quarks B-physics Gf Neutrino 0nubb, CP Sterile, LFV Inflation BAU

28 GUT LHC DM Quarks B-physics Gf Neutrino 0nubb, CP Sterile, LFV Inflation BAU

29 Summary The future direction of flavor model building will strongly depend on experimental results: atmospheric mixing, leptonic CP violation,mass hierarchy,... If the atmospheric angle is VERY close to be maximal, evidence of a neutrino mu-tau symmetry If the atmospheric angle is NOT maximal, even anarchy is possible BUT flavor symmetries imply testable mixing & mass sum rules

30 Summary In the multi-higgs case, hopefully LHC will give us some indication We can also have indications from Flavor Physics like B decays From the theoretical point of view, a possible criteria to proceed is to link very different topics and problems like dark matter and neutrino and so on...

31 Tri-bi-maximal mixing: theoretical ansatz tri-maximal solar angle reactor angle zero maximal atmospheric Angle